Piston for engines and process for the manufacture of these pistons



jun 24,1930.

R. DE FLEURY PISTON FOR ENG I NES AND PROCESS FOR THE MANUFACTURE OF THESE PISTONS Filed June 1, 1925 INVENTOR. H. De M @u W y BY,

ATTORNEYS.

Patented June 24, 1930 UNITED STATES RAYMOND DE rLEUnY, PARIS, FRANCE A PISTON FOR ENGINES AND PROCESS FOR THE MANUFACTURE OF THESE PISTONS Application filed June 1, 1925, Serial No. 34,257, and in France .Tu1y 2 1924.

The present invention has for its object a piston for engines. This piston is characterized by the fact that the bottom has a thickness which varies according to such a law that the ratio between the thickness at a point of the bottom and the distance from this point to the center of the bottom constantly decreases from the center towards the periphery.

Fig. 1 illustrates the geometrical diagram permitting the lay out of the profile of the inner face of the piston.

Figs. 2 and 3 show, in cross section, a form of construction of the piston.

It is already known that an elficient cooling of the piston necessitates opposite each concentric circle traced on the bottom, sections for the passage of heat equal to the absorption surfaces, that is to say to the surfaces of the concentric circles contemplated.

Such a condition necessitates, in first approximation, opposite each circle, a thickness of bottom proportional to the radius of the circle under consideration, by noting however that the distance travelled over by the heat being greater for pistons of large bore, it is necessary to provide, at peripheral contact, for a cooling equivalent to that of pistons having a small bore, a height say it proporso tionally greater for the first pistons than for the second pistons. In the same way, the height h, for the same efliciency and the same bore, can be smaller with a more permeable metal than with another metal which is not so good a conductor.

But it will be seen that in such an arrange ment, the distance to be travelled over offered,

per unit of section, to the absorbed heat, at each point of the bottom, is longer for the central portions of the bottom of the pistons than for the more peripheral portions and that it thus results therefrom a mean temperature higher as the center than at the periphery.

As in the working of an engine it is the local temperature of a hotter point which determines the perturbations and the limitations of speed (particularly with large bores) one increases, in accordance with the present invention, the security of working and the der small weights, permit to obtain large secengine will be able to work at a higher speed i by lowering the lower temperature of the center of the piston and progressively that of the concentric circles by offering to the absorbed heat, opposite each concentric circle which will give the inner appearance of an element having a torus or conical surface obtained by a convex generating line, at least in the case of a piston externally limited by a plane surface. 1

The advantage of such a profile consists in that it allows of constituting a piston bottom which, during working, will not presentthe mean minimum temperature, but the local minimum temperature for the minimum of,,80 materials used.

' Of course, the foregoing does not exclude the use of a conical surface, obtained by a convex generating line, the top of which would be truncated at the center of the bottom (Fig. 2) or even the utilization of a bottom having an external convex surface but presenting the same inner characteristics (Figure 3).

For pistons having externally bulged bottoms, the same law of variation of the thicknesses is applicable, by of course taking in account the increase of thickness produced by the bulged shape relatively to the flat bottom according to which it is projected on a plane at right angles to the axis of the piston.

The above mentioned shapes are particularly convenient for light metals which, un-

tions of conductibility.

What I claim as my invention and desire to secure by Letters Patent is:

An engine piston in which the bottom has a thickness varying according to such law that the ratio between the thickness, at a point of the bottom, and a distance from this point to the center of the bottom constantly decreases from the center towards the periphery.

In testimony whereof I have signed my name to this specification.

RAYMOND DE FLEURY. 

